Trouble with end mills?

[Durkee]

Any of you having trouble with the end mills you're getting back from your grinder. Maybe I can help you to explain to him what the problem is. Or what it is that you want the tool to do that is out of the ordinary. If you want it to cut something specific, you need to let the grinder know that. If you're not quite sure what you want, maybe I can put you in the right direction. Maybe a specific type of end mill would work better. There's a lot of people here that know what they're talking about. Now you have a place to talk about your tools.

[cncman]

I just started working with metal on my Vertical mill, how do I sharpen my end mills?

[Durkee]

It's a little more complicated than that, but I'll try. There are several different ways to sharpen one manually. A tool and cutter grinder works best. You can use a 1A1 wheel or some use an 11V9 cup wheel. I used to use an air bearing fixture to grind o.d.'s. You have a finger that stays lined up with the wheel. The table stays stationary. The fixture rocks back to allow the end mill to pass by the wheel w/o hitting. Then you rock the fixture forward toward the wheel while at the same time gently setting the flute of the end mill on the finger. Once the fixture is all the way forward, you pull the end mill through the air bearing until the end comes off the finger. Repeat for each flute. That was an extremely abbreviated course on the o.d. Most machinists, unless they have grinding experience or at least the right equipment find it more economical to find a grinding shop that is in the area. If you really want to know more, let me know.

[lstool]

I Just happen to have one of these end mill grinding fixtures laying around, I send my endmills out to be sharpened it is not cost effective for me to be grinding endmills. So if anyone is interested it is a Weldone endmill grinding fixture, Just place it on you magnetic chuck on your grinder, put on your cup wheel and your ready to go. I believe it is worth over $2000.00 new. I'd let it go for $450.00. if interested let me know I can send e-mail Pictures.
Lenny

[Durkee]

That's exactly what I was saying Lenny. Most guys like yourself that are into machining can make more money by sticking to what they know best and letting someone that is set up for it do all the grinding. That's a pretty good price for that fixture.

[HuFlungDung]

Hi Durkee,

I've got a beef with the general method that is standard for grinding a gash in the end flutes to make an slotmill "center cutting" The factory method seems to always be a gash with a perpendicular face, but this doesn't drill worth a crap: excessive wobbling of the cutter is common.

I take my brand new slot drills to the bench grinder (with a CBN wheel) and grind a rake face inside the flute, which morely closely approximates the actual helix of the cutter. This modified flute drills much better, with less clogging and wobbling.

Is this a particularly tough operation to program in today's cutter grinding equipment, or why do they persist in the "easy gash/crappy performance" method ?

[Durkee]

You make a good point. I don't have a good answer for you on that one. They normally gash a ball with some rake. I don't know why they are still grinding the end rake at zero. To be honest with you , we still grind them that way here, unless a customer lets us know that they are going to drill with it. Then we will make it for the material they are cutting. I guess that no one has put up a big enough fuss yet. I think we'll start griinding the end with a rake on it. Maybe it'll catch on, eh? How much rake do you normally like? I'm thinking that 7 degrees or so would be sufficient.

[HuFlungDung]

I don't have a ready method to measure the angle since I am doing this offhand, but generally, I try to follow the cutter's natural helix angle, so as not to spoil the nice smooth face inside the flute.

[Durkee]

The problem with going with that much rake is that as you grind the end back, you end up losing your center. Thus, it's no longer center cutting. I dont think that there's a need to over do it. 7 - 10 degrees should really be enough, then you will still have a center left in your end mill at the next re-grind without cutting the end right off and starting over.

[HuFlungDung]

You're the doctor

I've never had the problem that you speak of though. It must be due to the way that I am holding it, because the radius of the wheel sweeps out from the center, so there is always a thicker web anywhere from the point on back.

[Konrad]

Sometimes, like in this case, a good hand job is better then CNC.

It doesn't bother me that much with slot drills, its a millingcutter after all.
I usually peck down, not a problem for keyways.

I do the gash like, [webthinning] allot on drills when new.
A drill can remove metal faster then any other HSS bits.
Konrad

[brainlessme]

Hey guys...while on the rake issue...need some help on this one....
am working on a 15mm end mill solid carbide, six flute and corner radius of .40mm..... everytime we try to test it...it does fine for some jobs and then starts sparking which is not acceptable to the customer!! any leads on that,,,is it cos of the rake on the end face...i keep aroun 5deg, then i also have an axial rake at the end face of 2 1/2 deg... the corner radiu has just one relief ie 10deg...!!!
need some information on how much rake is good on an end mill!!!